On the basis of their electron configurations, predict the formula of the simple binary ionic compound likely to form when the following pairs of elements react with each other: a. aluminum, Al, and iodine, I \begin{tabular}{c} Al3I2 \\ \hline AlI4 \\ Al3I \\ All3 \end{tabular} b. strontium, Sr, and oxygen, O \begin{tabular}{|l} \hline SrO \\ \hline SrO3 \\ Sr2O \\ SrO2 \end{tabular} c. gallium, Ga, and nitrogen, N Ga2N Ga2N3 GaNGaN GaN3 d. radium, Ra, and hydrogen, H Ra2H Ra2H3 RaH2 RaH